The present invention relates to a navigation system and navigation equipment which present the location of a mobile unit or the like using map information which is provided over a communication network such as the Internet.
The present application claims priority from Japanese Application No. 2002-126940, the disclosure of which is incorporated herein by reference.
For example, in the field of the navigation technology for presenting the location of a mobile unit or the like, a conventional vehicle navigation equipment configured as shown in FIG. 6 has been used to provide the location of a traveling vehicle to a driver or a passenger in a vehicle.
That is, the conventional navigation equipment includes an information read unit 3 for reading information from a large capacity information storage medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc) on which stored are map data 1 to be displayed and road data 2 containing detailed information on many roads and intersections corresponding to the map data 1.
When a user such as the driver of a vehicle loads a DVD or the like into the information read unit 3 to issue a command to start navigational guidance, a GPS receiver 5 receives radio transmissions from a GPS (Global Positioning System) satellite 4 to determine a self-location of the vehicle. A position estimate unit 6 performs map matching between the location data indicating the self-location and the road data 2, there by estimating the accurate current position associated with reception errors or the like corrected. A display data generating unit 7 combines the resulting estimate with the map data 1, and the combined information is supplied to a display unit 8. In this manner, the current position of the vehicle is displayed in the form of a map.
The map data 1 is formed of image data which can visually be displayed in the same manner as maps of sheet type found in a so-called commercially available atlas.
On the other hand, the road data 2 is formed of a larger quantity of data than the map data 1. This is because the road data 2 is not intended merely for a visible representation of a map but also contains a large quantity of detailed data with regard to the orientation and distance of all the roads and the locations (latitudes and longitudes) and shapes of all intersections (e.g., the shapes of intersections with traffic signals or overpass crossings), which are contained in the map.
It has been a common practice to update such a large quantity of road data 2 and map data 1, for example, every time a new road is constructed, and store the updated information on a DVD or the like, which is then distributed to users, thereby providing an up-to-date navigational environment to the users.
However, the latest information provided in a DVD or the like is insufficient for dynamic navigational guidance. Accordingly, attempts have been made to provide the latest navigational environment as soon as possible by distributing the latest map information (i.e., map data and road data) over communication networks such as the Internet to the navigation equipment possessed by the users.
A so-called client-server system has also been suggested which not only distributes the latest map information but also receives the location data determined by a GPS determination from the traveling vehicle and then provides the user with the real-time map information (map data and road data) relating to the surroundings of the vehicle to display the current position of the user on a map at the user's navigation equipment.
However, as described above, the distribution of map information over a communication network such as the Internet would require the transmission of a large quantity of map data and road data to the user's navigation equipment. This has raised problems that a long transmission time is required, there by making it difficult to provide fast response sufficient for dynamic navigational guidance, and the user is burdened with an increase in costs for transmissions.